The present invention relates to a command multiplex number monitoring control scheme in an information processing system including a plurality of higher rank apparatuses and a storage apparatus connected via a network, and a computer system using this command multiplex number monitoring control scheme.
A storage apparatus connected to one or more higher rank apparatuses (hosts) via a storage area network (SAN) such as a fiber channel (FC) includes storage means (which is referred to as volume, and which typically includes a disk apparatus) having one or more logical units (LU) and a storage control apparatus for controlling the storage means. The storage control apparatus exercises control for permitting a command from a higher rank apparatus to access some of logical units included in the storage apparatus. The storage control apparatus includes one or more ports. A plurality of higher rank apparatuses are connected to one port via a network, and multiplex command processing is made possible.
In such connection, it is necessary to permit only a specific higher rank apparatus to access a specific logical unit included in the storage means. Each of the higher rank apparatuses has a world wide name (WWN) serving as an identifier. And for the purpose of access permission decision control, the world wide names (WWN) each of which is an identifier of the higher rank apparatuses and information concerning logical units by which the higher rank apparatuses are permitted to be accessed are set in the storage control apparatus. Hereafter, a higher rank apparatus having a WWN is also referred to simply as WWN in some cases.
A technique belonging to conventional techniques of this kind and having a function of preventing illegal access from higher rank apparatuses in an environment in which it is possible to physically accept access from all higher rank apparatuses is disclosed in JP-A-10-333839.
In such a computer system in which one or more higher rank apparatuses are connected to a storage apparatus via a network such as a SAN, a command issue multiplex number is set for each higher rank apparatus so as not to exceed a multiplex limit number of command processing in the storage control apparatus included in the storage apparatus. If the storage control apparatus receives commands exceeding a command processing multiplex limit number, then the storage control apparatus reports a status to the effect that the number of accepted commands (the number of queues) is full (hereafter referred to also as command full or queue full (QF)) to the higher rank apparatuses. Upon receiving the QF status, the higher rank apparatuses stop command multiplex issue, so that unexpected performance degradation is caused. For example, condition in which multiple processing of commands is not executed continues. In the configuration of the conventional computer system of this kind, there is nothing for avoiding such unexpected performance degradation but to add sufficient command processing resources.